1. Field of the Invention
The present invention relates to a liquid fuel injection system, and, more particularly, to a liquid fuel injection system comprising a double-structured fuel nozzle including a primary flame region located in the center of the fuel nozzle and a partial oxidation region formed by the partial oxidation of liquid fuel.
2. Description of the Related Art
Generally, methods of reducing nitrogen oxides (NOx) generated by burning fossil fuels may include a method of preventing the formation of nitrogen oxides by physically, chemically and biochemically by removing nitrogen components from fuel before the burning of fuel, a method of controlling the formation of nitrogen oxides during the burning of fuel, and a method of removing nitrogen oxides from exhaust gas after the burning of fuel.
Among the methods of reducing nitrogen oxides (NOx), since the method of controlling the formation of nitrogen oxides during the burning of fuel, in which a low NOx burner and multistage burning and reburning techniques are used, can relatively easily prevent the formation of nitrogen oxides (NOx) and can be applied to both the existing facilities and new facilities at low fixed investment costs and low operation costs, it is very economical, and is thus intensively researched and developed by advanced enterprises.
In a system for burning liquid and solid fuels, a burning technology for realizing low NOx is most important to control the formation of fuel NOx caused by the oxidation of nitrogen in fuel.
In the low NOx technology, the formation of fuel NOx is controlled by decreasing the conversion ratio of nitrogen (N) into nitrogen oxides (NOx) in fuel, and residence time taken to reduce NOx to N2 is controlled by clearly dividing a burning area into a rich fuel region and a lean fuel region and forming a fuel-air mixed area using rotating flow, thereby realizing ultralow NOx.
In most conventional liquid fuel burners, thermal NOx is reduced by decreasing a flame temperature using steam or latent heat of evaporation attributable to water injection, but the formation of fuel NOx in flame due to the nitrogen components in fuel is very remarkable, therefore these liquid fuel burners cannot completely reduce NOx. Further, in conventional multistage burners, since it is difficult to physically clearly divide a flame area into a rich fuel flame region and a lean fuel flame region, it is impossible to prevent the formation of a local high-temperature region in flame, and thus a relatively large amount of thermal NOx is generated. Currently, since the design technologies of new concept fuel nozzles and burners are insufficient, there is a problem that alternative technologies for remarkably reducing fuel Nox are not basically established.